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Chapter 7
Analyzing and Interpreting Quantitative Data
Power Point Slides by Ronald J. Shope in collaboration with John W. Creswell
Steps in quantitative analysis and
interpretation
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How do you prepare the data for analysis?
How do you analyze the data?
How do you report the results?
How do you discuss the results?
Educational Research 2e: Creswell
How do you prepare the data
for analysis? Inputting data
• Score data by assigning numeric codes
to responses
• Create codebook
• Use information from instrument when
possible as part of coding scheme
• Create data file in data grid
• Create variable, value labels
• Clean database, missing values
Educational Research 2e: Creswell
Determine types of Scores to
analyze
• Single item
• Summed scores
• Difference scores
Educational Research 2e: Creswell
Selecting a statistical
program
• Statistical Package for Social Sciences
(SPSS) most popular
• Other programs
– Mini-tab
– Statview
– SAS (JMP/JMPIN)
– StatPac
• Use mainframe, PC or Mac platforms
Educational Research 2e: Creswell
How do you analyze the data?
Conduct descriptive analysis
• Conduct descriptive analysis
– Measures of central tendency
– Measures of variability
– Measures of relative standing
Educational Research 2e: Creswell
Run Descriptive statistics
Descriptive Statistics
Central Tendency Variability
Mean
Median
Mode
Relative
Standing
Variance
Z-Score
Standard Deviation Percentile Ranks
Range
Educational Research 2e: Creswell
Conduct inferential analysis
• Hypothesis testing
• Confidence interval
• Effect size
Educational Research 2e: Creswell
Conduct hypothesis tests
• Identify a null and alternative hypothesis
• Set the level of significance (alpha level)
for rejecting the null hypothesis
• collect data
• Compute the sample statistic
• Make a decision about rejecting/failing
to reject
Educational Research 2e: Creswell
Computing the sample statistic
Inferential Statistics
Continuous (iv)
Continuous (dv)
Continuous (iv)Continuous (dv)
Continuous (iv)Continuous (dv)
Continuous (iv)Continuous (dv)
Chi-Square
Parametric
Parametric
Parametric
Nonparametric
Nonparametric
Nonparametric Analysis
Pearson
Correlation
Coefficient
Regression
Coefficient
T-Test
Spearman
Rho
Analysis
of
Kendall’s Variance
Tau
Analysis
of
Covariance
Mann- Discriminant Point
Witney Analysis
Biserian
U-Test
Correlation
Kruskall
Wallis
Test
Friedman
Two-Way
Anova
Educational Research 2e: Creswell
Phi
Coefficient
How to select an appropriate
statistic (see Table 7.5)
• Determine the type of quantitative research
question or hypothesis you want to analyze
• Identify the number of independent variables
• Identify the number of dependent variables
• Identify whether covariates and the number of
covariates are used in the research question
or hypothesis
Educational Research 2e: Creswell
How to select an appropriate
statistic (see Table 7.5)
• Consider the scale of measurement for
your independent variable(s) in the
research question or hypothesis
• Identify the scale of measurement for
the dependent variables (e.g.
continuous or categorical)
• Determine if the distribution of the
scores is normal or skewed
Educational Research 2e: Creswell
Normal Curve
34%
34%
13.5%
13.5%
2.5%
-3
2.5%
-2
Mean
+1
-1
Standard Deviations
Educational Research 2e: Creswell
+2
+3
The Normal Curve of Means Differences of
All Possible Outcomes if the Null Hypothesis
is True
Reject the
Null
Hypothesis
High Probability
Values if the Null
Hypothesis is True
Reject the
Null
Hypothesis
Extremely low
Alpha=.025 Alpha=.025
Probability Values
if Null Hypothesis
is True (Critical
Two-Tailed Test
Extremely low
Probability Values
if Null Hypothesis
is True (Critical
Region)
Region)
Educational Research 2e: Creswell
Outcomes of hypothesis testing:
Type I and type II errors
Decision made by
the Researcher
Based on the
Statistical Test
Value
Reject the
Null
Hypothesis
Fail to Reject the
Null Hypothesis
State of Affairs in the Population
No EffectNull True
Type I Error
(false positive)
(probability=
Alpha)
Correctly not
rejected
no error
Educational Research 2e: Creswell
Effect Exists
Null False
Correctly
rejected
no error
(probability=
power)
Type II Error
(false negative)
(probability=
Beta)
Other inferential tests
• Confidence intervals
• Effect sizes
Educational Research 2e: Creswell
How do you report the
results?
• Tables summarize statistical information
• Figures (charts, pictures, drawings)
portray variables and their relationships
• Detailed explanations about statistical
results
Educational Research 2e: Creswell
How do you discuss the
results?
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Summarize major results
Explain why they occurred
Advance limitations
Suggest future research
Educational Research 2e: Creswell